What options are available for extracting data for all ZIP Code® Tabulation Areas (ZCTAs™) in the nation?

SF1 and SF3 users can use American FactFinder, the National File data set in ASCII text data format or purchase either the National File or US Summary software version disc product. Data is not available for ZIP Code® Tabulation Areas from SF2 or SF4.

What options are available for extracting data for all census tracts, block groups or blocks (SF1 only) in the nation?

The best option, for most SF1 and SF3 users, is the US Summary software version disc products. Extracting data for census tracts (and below) from SF1 and SF3 with the ASCII text data files requires repeating the same process for each state or carefully combining the individual state data sets beforehand. The latter procedure would require creating a two key field consisting of STATE + LOGRECNO to link the data to the geographic identifiers (that identify the specific area). Either way, this can be a time consuming and error prone process.

SF2 and SF4 data users can use the National File data set in ASCII text data format or the National File software version disc product to extract data for whole census tracts only.

What is the difference between the US Summary File and the National File?

These distinctions apply to the original ASCII text data files and the DVD-ROM disc products only ; not to American FactFinder or DataFerret.

The National File contains data for larger geographic area types such as the United States, regions, divisions, states, counties, county subdivisions, places, metropolitan statistical areas, congressional districts (106th Congress), American Indian and Alaska Native Areas, and Hawaiian Home Lands. The SF1 and SF3 National Files include data for whole ZCTAs™ but does not include data for census tracts, census block groups or census blocks. The SF2 and SF4 National Files include data for whole census tracts only but does not include data for for ZCTAs™.

The US Summary File is a compilation of all of the individual state summary files in their entirety. It is available on software version DVD-ROM disc only. See Chapter 4 of the appropriate summary file documentation for a complete list of available summary levels (area types) for the State Summary files and the National File. This information is presented in separate charts.

Why am I seeing more than one record for the same area?

If more than one record appears for a specific area, that area has been split into parts for that summary level (see SUMLEV). This can be seen by looking at the codes for each element of the complete summary level description in Chapter 4 of the file documentation. The next question includes an example.

Also, some larger summary levels such as state or county totals also have data for geographic components of the area. This can be seen by looking at the left column of the summary level sequence charts in Chapter 4 of the file documentation. A look at the value of the geographic component variable GEOCOMP should clear up any remaining confusion. More information about this variable, including a code list, is available from Chapter 7 of the file documentation.

If a block crosses county subdivision and/or place boundaries, its' data are split into multiple records. This can be seen by looking at the value in the geographic identifier field for each element of the complete summary level description above. Each element in the above description is separated by dashes.

A specific combination of geographic identifier fields, based on the field SUMLEV (summary level), is used to identify a specific area and link data for that area to separate boundary files. This combination will include a numeric code or a number for each geographic element in the complete summary level description. See Chapter 4 of the appropriate file documentation for a complete list of summary level codes and descriptions.

ASCII text data file users will find the geographic identifiers (including SUMLEV) in the data set's geographic identifier file (which should initially appear last in the directory). The LOGRECNO field is used solely to link data files in a data set to the geographic identifier file within the same data set. LOGRECNO can not be used to link any file in the data set to any file outside the data set.

Software version disc users can select individual geographic identifier fields (including SUMLEV) from the Geographic Identifiers folder on the Simple Variables tab. Output data files created with the software will also include an automatically created field labeled KEY that contains a specific combination of geographic identifier fields based on the value of SUMLEV.

It is also a good idea to examine the GEOCOMP (geographic component) field after you have filtered the data by SUMLEV. If GEOCOMP does not equal "00", the data for that record is for a subset of the total area and/or population. See Chapter 4 (left two columns) and the Footnote Section of Chapter 7 (Data Dictionary) for a complete list of descriptions and codes for GEOCOMP.

Why do I get an error message when trying to create an output file with the Census 2000 Data Engine?

It is also recommended that users upgrading their operating system to Windows XP from a prior version of Windows implement a full installation of Windows XP from a Microsoft CD as opposed to from an image or "stamped" installation.

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